This invention relates to a dynamic damper for use with a rotary shaft. More specifically, this invention relates to a dynamic damper assembly having a plurality of mass members which are affixable in an assembled position to a rotary driveshaft for use on a motor vehicle.
It is known that rotary driveshafts and propeller shafts are often used in the power train designs of modem motor vehicles including automobiles. More specifically, it is known that rotary driveshafts are used to drive the front wheels of front wheel drive vehicles and propeller shafts are utilized in driving the rear drive system in rear wheel driven vehicles. In studying the rotational movement of the rotary driveshaft, it is known that certain unbalanced rotation may occur at certain rotational speeds. Undesirable vibrations may be induced into the rotary driveshaft as a result of an unbalanced rotation. These undesirable vibrations often present themselves as bending or torsional forces within the driveshaft during rotation.
It is obvious that bending or torsional forces due to the unbalanced rotation of the rotary driveshafts are not desirable or suitable in the operation of the drive train of most vehicles. It is known to utilize various dynamic dampers and mass dampers to suppress the undesirable vibrations that are induced in the rotary driveshaft due to the unbalanced rotation.
Dynamic dampers are often installed or inserted directly onto the rotary driveshafts. The dynamic damper is designated to generate a prescribed vibrational frequency adjusted to the dominant frequency of the excited harmful vibrations. The dynamic damper converts or transfers the vibrational energy of the rotary drive shaft to the dynamic damper by resonance, and eventually absorbs the vibrational energy of the rotary driveshaft. In short, the dynamic damper attempts to cancel or negate vibrations that are induced onto or caused by the rotary driveshaft in normal operation of the drive train of the vehicle.
It is understood that the ultimate design of front wheel drive rotary driveshafts often depend upon engine compartment space constraints set by the vehicle manufacturers. The eventual size and design of the dynamic damper must therefore be commensurate with the engine compartment design and other vehicle space constraints. Lastly, the dynamic damper must appropriately generate the specific harmonic frequency range that is required to counteract the undesirable vibrations of the rotary driveshaft.
In most powertrain and engine compartment designs, downsizing or reducing the size of most components, including that dynamic damper while still affording the proper horsepower or torque range is desirable. It is therefore important to have a dynamic damper which is as small in overall size as practical while still affording the correct vibrational counteracting frequency range of operation.
U.S. Pat. No. 5,056,763 to Hamada, et al. discloses a dynamic damper. The dynamic damper of Hamada, et al. comprises a pair of ring shaped fixing members spaced apart at a predetermined interval. The dynamic damper of Hamada is inserted onto and supported by the rotary driveshaft. A mass member is disposed between the pair of ring shaped fixing members. A pair of connecting members are then provided to connect the ends of the fixing members to the ends of the mass member. It is noted that the dynamic damper design of Hamada, et al. also requires individual metal clamps to be added on either side and over the ring shaped fixing members to operationally affix the dynamic damper to the rotary shaft. Further, it should be noted that the ring shaped fixing members are spaced apart from the mass member not only in a vertical but also in horizontal direction thereby increasing the overall size of the dynamic damper.
U.S. Pat. No. 5,660,256 to Gallmeyer, et al, addresses the above mentioned problems by providing a dynamic damper for absorbing vibrations in a rotary shaft. The dynamic damper comprises a mass member having an inner surface and an outer surface. A plurality of elongated connecting members extend radially inwardly from the inner surface of the mass member thereby defining a plurality of spaced apart attachment surfaces which directly contact the shaft. As disclosed, the mass member is cylindrical in shape and is of a press fit style which is directly installed around the outer circumference of a rotary driveshaft.
While the above referenced patent to Gallmeyer addresses and solves the problem of undesirable vibrations in a rotary driveshaft, the single piece press fit design requires installation at the time of assembly of the receiving drive shaft and before installation in a vehicle. In some cases, this requirement may cause additional and undesirable time and labor.
Consequently, a need has developed for an improved dynamic damper which may be installed subsequent to the assembly and installation of a receiving driveshaft.
According to the present invention there is provided a dynamic damper for absorbing vibrations in a rotary driveshaft, the dynamic damper comprises a mass member assembly including a plurality of mass members each having an inner surface and an outer surface. The damper also includes a plurality of elongated connecting members extending radially inwardly from the inner surface of each mass member thereby defining a plurality of spaced apart attachment surfaces. In one embodiment of the present invention, the mass members are affixable when assembled to the rotary driveshaft such that each of the plurality of spaced apart attachment surfaces contacts the rotary driveshaft. The mass member assembly is also spaced apart from the rotary driveshaft and is supported from the connecting members to allow the mass member to vibrate by resonance. The connecting members are thereby subjected to compression deformation between the mass member and the rotary driveshaft.
It is an object of the present invention to provide a dynamic damper which is compact in configuration while still generating upon rotation an inherent harmonic range to dampen the undesirable vibrations caused by the rotary driveshaft.
It is a further object of the present invention to provide a dynamic damper which allows for changes in the harmonic frequency range by adding or deleting a certain predetermined number of radially extending connecting members.
It is yet another object of the present invention to provide a dynamic damper which allows for changes in the harmonic frequency range of the dynamic damper through modifications in the lateral length of the connecting members.
It is yet a further object of the present invention to provide a dynamic damper wherein the rectangular connecting members are equally spaced apart from each other along the inner surface of the cylindrical mass member.
It is still a further object of the present invention to provide a dynamic damper wherein the connecting members are formed from the integral elastic material coating that covers the entire inner and outer surfaces of the cylindrical mass member.
It is yet still another object of the present invention to provide a dynamic damper wherein the mass member constitutes an insert and is molded integrally with the connecting members.
It is yet still a further object of the present invention to provide a dynamic damper which is affixable to a rotary driveshaft subsequent to assembly and installation in a vehicle.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.